The objective of our research is to relate the form and function of macromolecular assemblies which exemplify distinctive aspects of cellular organization. Coordinated X-ray diffraction and electron microscope studies are being carried out on lipid containing viruses to investigate the assembly of the viral envelope which is derived by differentiation of the host cell membrane. The molecular interactions that stabilize the myelin membrane structure are being characterized by coordinated X-ray and neutron diffraction studies on nerves which have been modified by in vitro treatment or by pathological conditions. The structural basis of electrotonic coupling between cells is being investigated by coordinated X-ray diffraction and electron microscope studies on isolated mouse and rat liver gap junctions. The regulatory interactions of the muscle proteins tropomyosin and troponin are being related to the structure of crystalline complexes of these proteins studied by X-ray diffraction. New X-ray and neutron diffraction techniques are being developed to investigate the molecular dynamics and structure of intact and reconstituted cellular assemblies.